Skt verse on poet, poetaster and plagiarist

[Mahinda Palihawadana]

Could any one help trace the source of the verse kavir anuharati-cchAyAm/
arthaM kukaviH/ padaM chauraH? (BTW this verse was used in a literary debate
called kukavi-vAda in 1930s in Sri Lanka, the controversial purist Sinhala
grammarian Munidasa Kmaratunga usng it to argue that the Sinhala scholar-
poet ZrI RAhula was a poetaster and not a real poet, because  many verses in
his works contained ideas borrowed from Sanskrit poetry.)
Thanks and best wishes.
Mahinda Palihawadana